Device for standardizing thermometers and other temperature measuring instruments



c. L. FRY ET AL 2,162,614 DEVICE FOR STANDARDIZING THERMOMETERS AND OTHER TEMPERATURE MEASURING INSTRUMENTS Filed Dec. 20, 1937 Patented June 13, 19 39 THEE TEMPERATURE MEASURING lNSTR-ULIENTS- Clovis L. Fry and Kalil-t alsignors Okla.

Robert w. was, El Dorado, to sreuy on Company, Tul ,v

Application December 20, 1937, Serial No. 180,900

. 2 Claims. Our invention consists in new and useful improvements in a device for standardizing-thermometers and other temperature measuring in struments, and has for its object to provide a device of this. nature which is simple in construction and which represents a distinct improvement tories employing temperature measuring devices 10 such as thermometers, thermocouples, resistan thermometers and thelike to check and standardize such measuring devices by comparison with a standardized have been calibrated with great care against the accepted standards, usually by the United States Bureau of Standards, so as to insure. accurate readings. This comparison is commonly made by immersing the measuring. instrument to be tested together with a standardized instrument go in a common medium held at a uniform temperature.

One form of comparing medium frequently used isa well-stirred liquid bath but it has. been found that such baths present a number of disadvantages. Forexample, they seldom maintain a uniform temperature throughout on account of convection currents induced by the application of heat at one point and heat losses at other points. Liquids are notoriously poor conductors of heat and furthermore they cannot beused to cover a wide range of temperaturesbecause of limitations imposed'by the freezing point and boiling point of the liquid employed.

It is therefore the primary object of our invention to provide a device for testing and standardizing thermometers or the like which definitely overcomes the disadvantages of the known types of device employing stirred baths.

It is known that metals, particularly copper and aluminum possess the property of rapid heat transmission through their mass, and heat applied to bodies of these metals at one point is very rapidly transmitted to all parts of the continuous piece. We have found that in this prop- 5 erty, metals are far superior to liquids no matter how well stirred. It is therefore an object of our. invention to make use of this property in a distinctly novel manner by employing a metal block as a comparing medium and embedding a standardized thermometer or other temperature measuring instrument therein, together with one ormore instruments of unknown accuracy-whose readings it is desired to calibrate.

With the above and other objects in view which 5 will appear as the description. proceeds, our ininstrument whose readings venues consists in set forth, illustrated the novel features hereinafter in the accompanying drawing and more particularly pointed out in the appended claims. Referring to like character designate .both views,

similar the in which numerals of 'parts throughout v Fig. 1 is a perspective view of one form oif apparatus for carrying out our invention, said view being partly broken away to illustrate the construction of the device, and

Fig. 2 is a transverse sectional In the drawing which, tration, shows a form of laboratory use in the checkin glass thermometers, I-

view of the same.

for the purpose of illusapparatus designed for g of mercury in representsa solid block of metal, preferably copper oraluminum which may be of any convenient shape or size, depending upon the typeof instrument to be calibrated, said block being drilled with holes 2 of the proper diameter ceive the thermometers with a depth of insertion a plurality of vertical and depth to resnug fit and at a for which calibration is ,de-

sired. We have found by experimentation'that a satisfactory depth for the inches. The holes may be holes 2 is about five spaced regularly throughout the blockor irregularly as we have found that no important ture reading is discernibleat any .block.

dilference in temperapoint in the l A layer of electrical insulating material 3 surrounds theblock l on its lateral sides for the purpose of providing a non-conducting base upon which to wind the heating element hereinafter described. This insulating material may comprise asbestos paper covered with alundumcement or other suitable material.

ment 4 consists preferably of strips of resistance ribbon or wire wound around the lateral sides of the block I on thenon-conducting base 3.

In constructing the heating given standardizing to select a coil having electrical element for any device, care should be taken characteristics to suit the voltage available and the maximum temperature desired in the block I.

experiments have shown that for peratures upwards of 900 F. in .the'blo For example, our

attaining temck l, a

continuous coil of chromel A ribbon of a width of inch and a thickness of .005 inch containing approximately eleven ohms resistance, is a sat? isfactory heating element where voltage of 110 to 120 is available. A heating element so construced has an electrical capacity of Returning to Fig. l of ing the heating coil 4 is a layer about 1000 watts.

the drawing. surroundof inert electrical pose of controlling the we have found that for accurate results, it is best to allow the block to assume a stationary temperature before making readings. Otherwise it is diflicult for the eye to follow the readings simultaneously. This procedure requires but a high grade high temperature insulating material few minutes at any setting of the rheostat. The 8 separating-theunit from the casing 1. A suittested thermometers are then calibrated in any ableiinsulatin'g' material for this purpose may be suitable manner so as to standardize them with the thermometer of known accuracy.

As before stated, the device illustrated and described above is a type suitable for testing merrock wool which preferably extends not only around the lateral sides of the unit but across. the bottom thereo x The casing I may be constructed oi transite board or other non-inflammable heat resistant material, and if desired, a cover (not shown) 'of the same construction may be applied, holes beeters, resistance thermometers, or any common --temperature measuring or controlling mechanism.

From the foregoing it is believed that the con- 5 struction and advantages of our invention may be readily understood without further description,

the block. The Insulated block I and casing I are preterably mounted on a suitable base which also medium of binding posts H and I! which extend through the wall of the casing '1. Although we spirit of our invention as set forth in the followhave shown the rheostat Ill mounted on the base ing claims. 7 a l 9, it will be obvious that it may be placed at any What we claim and desire to secure by Letters convenient location where it will serve the pur- Patent is:

heat applied to the block I so that comparisons of the thermometer readings may be made at any predetermined temperamay be tested at one time depending upon the number of holes available in the block I. it'is desired to'test a thermomet r with'a length than. the-predetermined depth of I heating means, and a heat insulating casing for said block.

2. A self-contained testing apparatus for tem- 'ancl said casing.

CLOVIS L. FRY. ROBERT W. LESLIE. 

